(1) Field of the Invention
This invention relates to a scanner, in particular to the light source of the scanner.
(2) Description of the Related Art
In the optical system of a scanner, the light source module can be subdivided into a "light source module" and a "lens module". The light source module refers to the light source components including the light source and the base for supporting the light source. The lens module is to process the light ray with imaging signal including reflecting mirrors and focusing lens, etc. Conventional light source module and lens module are fixed with respect with each other.
FIG. 1 shows the top view of a typical optical module. The light 16 is mounted on an L-shaped base 12 by means of two bracelets 18 as shown in FIG. 2, which is the side view of FIG. 1. The L-shaped base 12 is mounted over the lens module 10. The light source scans and irradiates document 50 placed over a scan window 20 and produces a reflected light ray to pass through the light slot 14 on the lens module 10. As shown in FIG. 2, the reflected light ray 22 through the light slot 14 contains image signal and is reflected by the mirror 102 for further signal processing.
The L-shaped base 12 has a vertical flange. While the flange can reinforce the base to prevent bending and concentrate the light intensity to prevent scattering, the vertical flange protrudes upward toward the scan window 20 typically to an elevation higher than the brackets 18 as shown in FIG. 2. Due to manufacturing variations, allowance must be made to tolerate the any variations in the dimensions of the different components in the light source module and the lens module. In a practical design, the highest point in the light source module must clear the bottom of the window 20 by 3 mm. Otherwise, when the optical module scans the document back and forth, the top of the L-shaped base 12 may scratch the bottom of the scan window and the optical module may even be blocked. As shown in FIG. 2, the distance 66 is the minimum distance of 3 mm allowed for variations in mechanical dimensions of the different components. In practical scanners, the 3 mm allowance is barely enough to prevent scratching.
Such an allowance is not desirable, because the light source 16 must be moved away from the scanned document and is weakened as it irradiates the document.